The investigators have placed Yevtushenkov under house arrest.

Sistema, which controls Russia's biggest mobile phone company MTS , said it considered the accusations baseless.

More details on Sistema's holdings and structure follow below:

Sistema, incorporated in 1993, says it is Russia's largest publicly listed holding company. It is listed in Moscow and also has global depositary receipts listed in London.

The group had revenue of $35.9 billion in 2013 and operating income of $5.7 billion, according to company data. The group's website says Sistema is one of Russia's top 10 companies by revenue.

Chairman Yevtushenkov owns 64.2 percent of Sistema shares and is ranked as Russia's 15th richest man by U.S. magazine Forbes, with estimated wealth of $9 billion.

A more than 30 percent drop in Sistema's shares in Moscow on Wednesday wiped more than $2 billion from the company's value.

The company's holdings include stakes in predominantly Russian businesses across a range of industries, including telecommunications, oil, utilities, consumer and high-tech. Sistema has a controlling stake in most of its interests.

Sistema's main holdings

MTS – Russia’s top mobile phone operator by subscriber numbers and revenues. Sistema has an effective controlling stake in MTS of 53.46 percent. MTS is listed in New York and Moscow.

MTS' operating profit in 2013 was 101.8 billion rubles (2.65 billion US dollar) compared to 93.8 billion rubles a year earlier. Revenue rose 5.3 percent to 398.4 billion rubles.

Bashneft – Russia’s sixth-largest oil company by output. Sistema bought into Bashneft in 2009 and directly owns almost 72 percent of Bashneft's voting shares and an overall stake of about 86.7 percent. Bashneft had been considering listing up to $2 billion worth of shares in London as early as this September. But Sistema was restricted from selling due to an investigation.

Bashneft's operating profit in 2013 was 81.4 billion rubles compared to 80.6 billion in 2012. Revenue rose 5.8 percent to 563.3 billion rubles.

Other holdings (not publicly listed)

Bashkirian Power Grid Company

Sistema Shyam TeleServices Ltd - mobile operator in India

Sistema Mass Media

RTI - IT, high-tech

Binnopharm - drugs manufacturer

MTS Bank

Detsky Mir - Russia’s top children’s goods retailer

Intourist - hotels operator

Medsi - one of the biggest private clinics chain in Russia

RZ Agro Holding - grains producer, a joint-venture between Sistema and Louis-Dreyfus family

United Petrochemicals Company

SG Trans - liquefied petroleum gas transportation services

NIS - Navigation Information Systems, a systems integrator for the GLONASS satellite technology adoption projects

Targin - oil services company in Bashkortostan near the Ural mountains

(Source: Sistema website: www.sistema.ru)

(1 US dollar = 38.3820 Russian rouble)

(Compiled by Maria Kiselyova in Moscow and Jane Merriman in London)

Stocks treated in this article : AFK Sistema OAO, ANK Bashneft' OAO